DALLAS — Many people have been wondering what those mysterious rings are that have shown up on the weather radar in recent days. Nope, still not aliens! The answer is much more terrestrial.
Roost rings
You probably haven't been looking at the radar recently since, well, we haven't needed to. The rain has left us once again. But if you did happen to look at the radar the last several mornings, you may have seen some mysterious 'rings' show up around sunrise and disappear over DFW.
These rings show up as a circular pattern that spreads outward over time before disappearing.
In the video below, you can see 3 rings:
- A large one north of Fort Worth
- A large one near Frisco
- Look closely and there's another one near Azle
What is a roost ring?
There's a simple answer for what causes these: Birds.
The radar is actually detecting a massive flock of birds taking off from a communal roosting site around sunrise. Exact numbers are unknown, but these birds are likely numbering in the thousands, maybe even millions.
When the sun rises they simultaneously take flight to begin their search for food. As they depart in different directions, the radar picks up their movement, creating a distinctive ring shape as they spread out.
Why do they form?
The doughnut shape that creates a roost ring is due to the way birds depart their roost. They tend to fly away in all directions, creating a circular pattern.
As the birds climb to higher altitudes or fly out of the radar's range, the ring fades away.
What type of birds are they?
In this example over DFW, I'm not quite sure.
However, given the time of year and the location of the rings, it is likely either blackbirds, starlings or grackles.
During the summer months, purple martins can show up creating roost rings, but those are typically found in more rural locations or near bodies of water.
Bats can also create roost rings, but they appear at sunset instead of sunrise.